Concertina

(Credit: The Concertina Museum)

This is an accordion-like musical instrument, meant to be played between the hands. It has buttons on either side, but, unlike an accordion, it does not have a keyboard.

Why I Looked It Up

In Once Upon a Tome:

Not a week passes by when he doesn’t come up to the shop floor to show me something esoteric, unfolding a gigantic map like a concertina…